Insert this script into a script editor (in between a script-tag <script type="text/javascript"> ) to change the default label into a custom one.

changeDiscussionLabel.js

//self-executing anonymous function
(function () {
    // String overrides
    function DiscussionListViewStringOverride() {
        Strings.STS.L_SPDiscHeroLinkAltText = "New Label"; //change "New Label" into your desired one, eg. "Create News"
        Strings.STS.L_SPDiscHeroLinkFormat = "New Label"; //change "New Label" into your desired one, eg. "Create News"
    }

    DiscussionListViewStringOverride();
    ExecuteOrDelayUntilScriptLoaded(DiscussionListViewStringOverride, "strings.js");
})();